Our goal is to identify the neuroanatomical pathways that mediate pheromonal responses in humans. We have determined that women are most senstive to putative pheromones in the late follicular and periovulatory phases of their menstrual cycle. We will use Positron Emission Tomography to study the functional neuroanatomy of the response to olfactory stimuli at that time and determine whether there is evidence for an accessory olfactory system, distinct from the main olfactory system. The role of the CRC will be to collect blood and urine samples and run or provide support for the assays needed to verify menstrual cycle phase.